The present invention relates to a quartz vacuum gauge utilizing a temperature-sensitive quartz resonator for continuously measuring gas pressure in the range from atmospheric pressure (10.sup.3 Torr) to lower pressure (about 1 .times. 10.sup.-4 Torr).
Generally, a vacuum gauge of the thermal-conduction type such as a Pirani vacuum gauge is used for measurement of the gas pressure in middle and low pressure range (10.sup.-4 to 10.sup.-1 Torr), but this type does not have sufficient sensitivity over gas pressure range of 10.sup.-1 Torr and therefore cannot be used over 10.sup.-1 Torr.
On the other hand, recently there has been developed another type of quartz vacuum gauge utilizing dependency of the resonant resistance of quartz resonator on surrounding gas pressure (hereinafter, referred to as a "quartz friction vacuum gauge"). The quartz friction vacuum gauge can be used to measure the gas pressure in the range from 10.sup.-2 Torr to atmospheric pressure.
Namely, the quartz vacuum gauge of the thermal conduction type has high sensitivity in the lower gas pressure range, but cannot effect measurement in the middle to atmospheric pressure range, while the other quartz friction vacuum gauge can measure the gas pressure in the range from atmospheric pressure to 1 .times. 10.sup.-2 Torr, but cannot be operative in the lower gas pressure range. Neither of the thermal conduction type quartz vacuum gauge or the quartz friction vacuum resonator by alone cannot satisfy the practical need of measuring continuously the gas pressure in the range from the atmospheric pressure to 1 .times. 10.sup.-4 Torr in a production process such as a semiconductor fabrication process.